doc manual noteworthy diff from C: division (JuliaLang#38174)

doc/src/manual/noteworthy-differences.md

@@ -285,6 +285,10 @@ For users coming to Julia from R, these are some noteworthy differences:
     literals are rounded (and not promoted to the `BigFloat` type) if they can not be exactly represented.
      Floating point literals are closer in behavior to C/C++. Octal (prefixed with `0o`) and binary
     (prefixed with `0b`) literals are also treated as unsigned (or `BigInt` for more than 128 bits).
+  * In Julia, the division operator [`/`](@ref) returns a floating point number when both operands
+    are of integer type.  To perform integer division, use [`div`](@ref) or [`÷`](@ref div).
+  * Indexing an `Array` with floating point types is generally an error in Julia. The Julia
+    equivalent of the C expression `a[i / 2]` is `a[i ÷ 2 + 1]`, where `i` is of integer type.
   * String literals can be delimited with either `"`  or `"""`, `"""` delimited literals can contain
     `"` characters without quoting it like `"\""`. String literals can have values of other variables
     or expressions interpolated into them, indicated by `$variablename` or `$(expression)`, which